Topic - problems with flac sound streams in containers

There are mplayer and Debian Linux "lenny".
And I have a problems:
1.I use matroska and ogg containers with video and number of different language sound streams.
There are problems with flac sound strams.
Mplayer sees only first sound stream in
container.
Neither intractive "#" command or options "-alang" ("-aid") not cause any result.
Player handle ogg or aac sound strem rather properly.
2.When ogg container flac sound become behind of
video more and more during movie.
Please help. What must I do?